The invention relates to a stirling engine with a variable stroke adopted for use on carriers as a driving source, particularly to a stirling engine with a variable stroke controlling output power by altering the contact position between a piston connecting rod and a swash plate.
In the four-cylinder double acting stirling engine the swash plate is a critical transmission component. It transforms the reciprocal motion of the connecting rods of four cylinders to rotation of the output shaft. The generator driven by the engine output shaft must maintain a steady rotation to avoid unstable power supply frequency or voltage and prevent a drop of power supply quality. Output power of the stirling engine is based on a full load condition. When the load changes, the rotation speed of the engine changes. As a result, the quality and stability of power generation are affected.
To employ the stirling engine directly as the driving source of a carrier, the main purpose is to minimize the use of special material and unconventional oil seals for the rotary shaft and expensive pressure control systems, and to avoid design of a heating pipe with a complex exterior profile (which is expensive in assembly and soldering). Further, to use low cost air preheating. The material problem has been solved because of a special alloy CRM 6D (developed by Chrysler in 1963). The oil seal and pressure control problems are still severe due to leakage of the oil seals during reciprocal sliding movement. Much high pressure gas tends to leak into the crank shaft box. The gas must be collected and compressed to be channeled back to the work area of the engine. The leaking of high pressure gas through the oil seals of the rotary shaft to the crank shaft box is the most difficult problem. In order to control the engine power by altering the gas pressure, pressure boosting in the crank shaft box also has to be made swiftly. However, such a practice causes leaking of lube oil from the crank shaft box under high gas pressure. This is still a problem without effective solutions. Moreover, a duplex pressure control system is very expensive. This counts especially for a double-acting circulatory engine. Therefore, adopting the design of a constant engine operating pressure and variable piston stroke to control engine output power not only can alleviate the air pressure problem of the oil seals, the leakage problem of lube oil due to rapid change of operating pressure can also be avoided.
To maintain the stability of engine operation, engine output power must be changed according to load-variations. To change the engine output power under constant rotation speed, the main approach is to alter the moving stroke of the engine piston. By doing so, the torque is changed to control the output power. Hence, by adopting a mechanism of variable piston strokes on the swash plate (to alter the output torque of the engine) output power is also controlled according to load- variations.
The primary object of the invention is to provide variable strokes for engine operations. In view of the difficulty involved in direct altering of engine operating pressure, the design of the invention aims at altering of the engine torque. As the swash plate is the main transmission mechanism of the stirling engine, the variable engine stroke may be altered by directly controlling the angle of the swash plate. While such a design can harness the motion displacement of the piston connecting rod, it is more complicated in fabrication and assembly. Therefore this invention provides a new control method that effectively controls the piston motion stroke during the transmission process (between the piston and the swash plate, while the engine is operating without changing the moving angle of the swash plate).
The invention adopts an approach that directly changes the contact position of the piston connecting rod and the swash plate without altering the angle and position of the swash plate. Thereby, the invention enables the connecting rod to form different perimeter tracks of movement on the swash plate and generate different height variations.
The stirling engine of the variable stroke of the invention has a rotary shaft, a swash plate, an adjuster, a piston and an actuator. The swash plate is a plate partly connected to the rotary shaft. The adjuster clips the peripheral rim of the swash plate. The piston has a piston connecting rod moving reciprocally and linearly to provide a driving power. The piston connecting rod is connected to the adjuster. The motion of the piston drives the adjuster, to move linearly. As a result, the swash plate is driven to rotate the rotary shaft. The actuator can change the clipping position of the adjuster on the swash plate, thereby results in different perimeter tracks of the motion of the connecting rod on the swash plate. Different height variations are generated to alter the piston stroke.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.